Flexibly divided silk screen

ABSTRACT

A framed silk screen for application of two or more colors, said screen having a thin, flexible divider strip which separates adjoining color areas. The lower edge of the strip is held by a bonded joint to the silk screen. A method for making the framed screen provides forming a linear pervious area in the screen, mounting the strip so that its edge is aligned with the pervious area, and bonding the strip to the screen by means which allow bonding material to pass through the pervious area of the screen.

United States Patent 541,720 6/1895 Clement 1,892,083 12/1932 SidebothamInventor Roy M. Harwell, Jr.

747 St. Michael: Lane, Gastonia, N.C.

28052 Appl. No. 829,318 Filed June 2, 1969 Patented June 29, 1971FLEXIBLY DIV IDED SILK SCREEN 9 Claims, 8 Drawing Figs.

U.S.Cl 101/127.1, 101/115, 101/202 lnt.Cl 84in l/24 FieldofSearch101/115,

References Cited UNITED STATES PATENTS 2,210,633 8/1940 Van der Reis101/115 2,718,326 9/1955 Le Blanc 217/22 X 3,078,793 2/1963 Jaffaet a1.l0l/l27.l

3,082,139 3/1963 Clark 156/153 3,370,977 2/1968 Anderson et al 156/153 XFOREIGN PATENTS 1,202,294 10/1965 Germany 101/115 PrimaryExaminer-William B. Penn Assistant Examiner -E. M. Coven AnorneyDominik, Knechtel & Godula ABSTRACT: A framed silk screen forapplication of two or more colors, said screen having a thin, flexibledivider strip which separates adjoining color areas. The lower edge ofthe strip is held by a bonded joint to the: silk screen. A method formaking the framed screen provides forming a linear pervious area in thescreen, mounting the strip so that its edge is aligned with the perviousarea, and bonding the strip to the screen by means which allow bondingmaterial to pass through the pervious area of the screen.

PATENTEDJUNZQ 1971 fa-Ja a 4.. A e

INVENTOR ROY M. HARWELL J'K FIG. 8

FLEXIBLY DIVIDED SIlLlli SCREEN This invention relates to a frame silkscreen in which a plurality of colors may be employed by using one ormore thin, flexible separator strips; and the invention also relates toa method for making such framed screens.

Silk screens are recognized and comprise a part of known silk screeningprinting including manual fixtures and machines. Pigment or ink isdeposited on such a screen and forced through image or fluid previousareas by the action of a member such as a squeegee. Flat screens whichare used in such machines have a continuous frame which may comprise aplurality of wooden or metal frame members to .circumscribe variousareas, commonly a rectangular area. Such screens may be maintainedstationary in the machine or fixture for flat printing while thesqueegee moves over the ink deposited on the screen from an inkreservoir of the like. Such flat screens may also be linearlydisplaceable relative to a cylindrical surface while a squeegee remainsstationary for moving the ink through the image areas of the screen.

The image or fluid pervious areas may be obtained in various ways onsuch screens, including masking portions of the screen intended tocomprise image areas, and then varnishing the screen. The nonmaskedareas will of course be fluid pervious. Cut screens may also be used.Photosensitive emulsions may also be applied to the screen in a lightpattern directed to those parts of the screen which are intended to befluid impervious. The masked or blocked portions can then be renderedfluid pervious by photographic processing. This may be done by knowndirect, indirect or indirect-direct methods. In the pursuit of the goalof screen printing by applying twoor more colors'with the same screen,rigid separators have been em ployed. Problems have arisen because thescreen flexes during printing which leads to ink bleeding or passingthrough a parted area between the rigid separator and the screen. Theuse of such rigid separators in the silk screening process has thereforeled to problems which has seriously limited their application andacceptance.

It is accordingly one object of the present invention to provide a framescreen in which a multiplicity of colors may be applied by utilizing animproved flexible separator strip mounted in an improved manner to theframed screen.

Another object is to provide a framed screen having a thin, flexibleseparator strip which can flex with the screen during the printingoperation without parting from said screen.

Yet another important object is to provide a framed screen in which athin, flexible plastic strip is employed which is inert to ink solvents,and which strip is mounted to frame members and bonded to the silkscreen in an improved manner.

Still yet another important object of the invention is to provide adivided framed silk screen in which a thin, flexible, plastic separatorstrip is mounted to the screen to separate color areas, and in which thelower edge of the strip is coincidental with a linear pervious area inthe screen so that bonding material may pass through said pervious areasto more effectively form a bonding joint between the silk screen and theseparator strip.

A still yet another important object of the invention is to provide amethod for making framed and divided silk screens in which a thin,flexible plastic separator strip is mounted in an improved manner tospaced frame parts of the screen and to the screen itself. This objectis attained by steps which allow the flexible strip to be securelymounted to the frame members, and to be bounded to the silk screen in animproved manner.

Still yet another object of the invention is to provide a method forobtaining improved divided framed screens by steps of roughening alongitudinal area of the flexible strip ad jacent the screen so that anenhanced bonding joint is obtained. A feature of this object is toprocess the screen so that a linear pervious area is obtained adjacentthe lower edge of the flexible strip, wherein bonding material passesthrough said linear pervious area to lock the bottom edge of theroughened flexible strip more securely to the screen itself.

The foregoing objects are attained together with still other objectswhich will occur to practitioners from time to time by the inventionwhich will now be disclosed, such disclosure including drawings wherein:

FIG. 1 is a perspective view of the framed and divided screen;

FIG. 2 is a top plan view of the framed and divided screen;

FIG. 3 is a side elevational view of the screen of FIG. 1;

FIG. 4 is an end view of the screen of FIG. 1;

FIG. 5 is a portional section view, on an enlarged scale, along line 5-5of FIG. 2;

FIG. 6 is a portional side elevational view of the separator strip usedin the divided silk screen of FIG. 1;

FIG. 7 is a portional side elevational view of a flexible, separatorstrip showing a roughened area which may be obtained in alternativeways; and

FIG. 8 is a portional top plan view showing an alternative embodimentfor securing the ends of the thin flexible strips in parts of the frameand the divided silk screen.

The framed and divided silk screen shown in FIGS. 1 and 2 has agenerally rectangular frame 8 which includes spaced longitudinal sidemembers 10 and 12 joined at their respective ends to shorter transverseend members 14 and 16. The respective ends of the side and end membersare shownjoined by a splice or rabbet joint 18. The joint may bevariously formed including a 45 bevel, or the like.

The side and transverse members are shown as being substantiallyrectangular in cross section although the frame members may be variouslyshaped to satisfy particular printing requirements, such as seating thedivided framed screen in a particularly screening machine. Theillustrated frame member is shown to consist of frame parts joined bysplices or the like, but an integral frame unit could also be provided,and such frame may circumscribe areas other than rectangular. The framemembers may be selected from a variety of materials including wood,aluminum, plastic and others.

The illustrated screen circumscribes. a rectangular area. The screen 27is stretched over said area and is tautly mounted by means shown asstaples 25, although other fasteners and bonding materials may be used.While reference is particularly made to a silk screen herein, it will berecognized that other screen fabrics may be employed such as nylon. Ingeneral, the principles of the present invention apply to any equivalentscreen materials which may also include stencils made from a variety ofmaterials. The term silk screen is intended to include such equivalentscreening materials.

The illustrated screen 27 is divided into parts or areas 28 and 28a by athin, flexible separator strip 30. Such strip completely divides thescreen area by extending to opposite end frame members 14 and 16. Theopposite ends of the separator strip are shown as received in slits 32in end member M and 32a in end member 16. The slits are dimensioned toreceive the thickness of the strip ends in close-fitting proximity. Ingeneral, the width of such slits are greater than the width of theseparator strip but preferably less than two times the width of suchstrips. The ends of the separator strip 30 are secured to the oppositeend members by fastening means shown here in end member 14, ascomprising fasteners or nails 34, 36 passing through opposite sides ofthe strip end in the slit at the top of the end members; and anotherpair of fasteners or nails 34a, 36a passing through opposite sides ofthe end of the strip at the bottom of the end members. Similar fasteningmeans are provided at end member 116, but such will not be described indetail. The strips may be otherwise mounted to the frame parts, forexample, by angle brackets, mounting blocks, clamps which are fastenedto the frame by bolts, or the like. In general, the strip ends are heldbetween spaced members with the aid of fasteners, a clamping action orthe like.

Looking now at the enlarged scale sectional view of FIG. 5, thetscreeri27 is diagrammatically illustrated as having an image or liquid perviousarea 37 between the bordering vertical lines and a linear pervious area37a adjoining the bottom edge of the separator strip 30. The linearpervious area extends along the length of the silk screen and saidlinear pervious area will form a junction line which will becoincidental with the separator strip following mounting thereof withinthe frame. The separator strip 30 is shown secured to the silk screen 27by a bonded joint shown generally as 38. The bonded joint is illustratedas having opposite chamfered sides 40 and 42, as well as a bulging base44. The bonded joint is formed preferably by a flexible resin bondingmaterial, although more rigid bonding materials are also operable tosome extent. The bonding material is preferably applied to oppositesides of the separator strip adjacent its lower edge, whereupon some ofsaid resin material passes through the linear pervious area 37ato formthe bulging base 44 following curing. An epoxy adhesive material hasbeen found useful for this purpose for example, Epon 828 cured by V-4Oagent, both supplied by Shell Chemical Co., Plastics and ResinsDivision.

An important feature is the provision of a longitudinal roughened area,shown generally as 46, adjacent the bottom edge of the separator strip.Such a longitudinal roughened area provides an increased irregularsurface area to attain better bonding action with the bonding materialused. In the view of FIG. 6, the roughened area is indicated ascomprising a pierced hole 48 having projecting broken flange portions50. A plurality of such pierced holes are preferably aligned in a row asindicated in the view of FIG. 6. The bonding action will thereforeextend coextensively with the row or pierced holes to the opposite endframe members. Polypropylene and nylon are useful materials to make theseparator strips. it will be evident that other thermoplastic, as wellas thermosetting materials, are likewise operable for making such stripsso long as the resulting strip is flexible and is inert to the solventscommonly employed in the printing inks.

The longitudinally roughened area is diagrammatically represented at 5 3in the view of FIG. 7, and this representation is intended to depictvarious mechanical and chemical roughened areas. Such roughened areamay, for example, be mechanically roughened by an abrasive such assandpaper. It may be roughened by knurling to obtain a plurality ofirregular peaks and valleys. The area 54 may also be chemicallyroughened by contacting the area with chemicals which partially dissolveand break up the surface, such as various mineral or organic acids. Achemical etchant may be employed which is composed of about 120 parts ofwater, about 1,500 parts of sulfuric acid and about 75 parts of analkali bichromate. A primer chemical solution may also be used tochemically roughen the longitudinal area 54, and one such composition isprovided under the trademark Hercoprime A T by the Hercules Company ofWilmington, Delaware.

The view of FIG. 8 illustrates an alternative embodiment for securingthe ends of the separator strip to opposite frame parts of the screenassembly. The end of the flexible separator strip 56 is shown secured toa frame member part 58. The end of the flexible separator strip has aloop 60, and the end of the separator strip is received in a straightslit or groove 62 and in a substantially circular passageway 64 in theend member 58. A complementary insert, such as a peg or dowel, is placedin the circular passageway to secure the end of the strip in the framepart.

A method for making the framed divided screen with the thin flexibleseparator strips includes the steps of preparing the screen 27 so that alinear pervious area 37a is formed thereon. This is preferably doneafter the screening material is mounted by stapling or the like to theframe. Such screen may be coated with a photosensitive emulsion and thenexposed with a positive element having a black line so that the lightdoes not fix the corresponding longitudinal area on the screen. When thescreen is processed by washing, the linear pervious area is obtained asan open image which extends the length of the screen. One end ofa thinflexible plastic strip, which may be nylon of about 0.015 inchthickness, is then roughened along its lower edge, placed in a slit inone frame part, and fastened to the frame member. The strip ispreferably softened by exposing the strip to warm air or the like, andthereafter the strip is placed under tension by stretching. This may bedone by pulling the free end toward the slit in an opposite frame part.The opposite free end of the strip is then securely attached in suchopposite frame part. The bonding material is then applied to theopposite sides of the lower edge of the strip which has been previouslyroughened to obtain the longitudinally roughened area. The bondingmaterial will move through the linear pervious area to attain bondingaction at the bottom edge of the flexible separator strip. To attain thetension of the strip by stretching, it is desirable to employ athermoplastic material such as polypropylene which softens in asufficiently warm environment to attain the stretching thereof. Warm airmay be used as described, or the stretching operation may be employed inan oven. No critical temperature levels are required since thermoplasticmaterial need only be slightly softened to attain the tension bystretching. It will be realized that some materials may be stretched atroom temperature. Strips may also be mounted without stretching.

The separator strip has been illustrated as providing separated colorareas by extending to opposed frame parts, but the strip may beotherwise disposed and fastened to parts of the framed silk screen toeffect such colorarea separation. The strip may be arcuately conformedand attached at its ends to spaced frame parts other then apart.Likewise strip parts may be joined at spaced points to sides of acontinuous member within the screen. Such a member may have a circularwall defining an image area through which pigment is moved to form acircular ink image. The strip parts may be joined to the wall at one oftheir ends, and to opposite frame parts at the other of their ends.Similarly, the strip parts may be partly fastened to one another toprovide angular and curvilinear patterns for the separated color areas.All such fastening points may be considered as frame parts for purposesof the present description. It will be understood that the term linearpervious area" will likewise include such angular and curvilineardispositions when used in describing the image areas of the screens.

The invention may now be practiced in the various ways which will occurto practitioners, and it should be understood that all such practicewill comprise a part of the present invention so long as it comes withinthe terms of the following claims. I

What I claim is:

l. A color-separating framed silk screen including a continuous framewhich forms a circumscribed frame area,

a silk screen secured to said frame and stretched over saidcircumscribed area, said screen having areas which are pervious andimpervious to fluid material,

a thin flexible, elongated separator strip fastened to parts of theframe and having a bottom edge secured to the screen to provideseparated color areas,

one of said fluid pervious areas being a linear pervious area in thescreen adjoining the bottom edge of said strip, said linear area beingpervious to a fluid adhesive material, and

a bonded joint formed by said cured adhesive material holding saidbottom edge to said screen by extending into said linear pervious area.

2. A framed silk screen as in claim 1 wherein said bonded jointcomprises a cured flexible resin, and said flexible resin bonded jointextends continuously along said bottom edge and linear pervious area.

3. A framed silk screen as in claim 1 in which said strip extends toopposite frame parts, and the opposite ends of said flexible separatorstrip are fastened to said opposite frame parts.

4. A framed silk screen as in claim 1 wherein said flexible separatorstrip is a plastic strip which is substantially inert to printing inkwhich contacts said strip.

5. A framed silk screen as in claim 1 which further includes a roughenedarea along the lower edge of said flexible separator strip to increasethe surface area to enhance the bonding action at said bonded joint.

6. A framed silk screen as in claim 1 wherein said frame is rectangularand includes a plurality of frame members comprising longitudinal sidemembers joined at their opposite ends by shorter end members, therespective ends of said members being spliced to one another,

said silk screen having a rectangular area, a slit provided in each ofthe opposite end members, the opposite ends of said flexible separatorstrip extending into said slits and being fastened therein, and

said bonded joint holding said bottom edge of the flexible separatorstrip to the screen, said bonded joint extending continuously betweensaid opposite end members.

7. A framed silk screen as in claim 5 wherein said roughened area alongthe bottom edge of said flexible separator strip to increase the bondingarea comprises a row of holes with projecting, broken flange portions.

8. A framed silk screen as in claim 5 wherein said roughened areacomprises an irregular rough surface.

9. A framed silk screen as in claim 8 wherein said roughened area is aknurled surface having a plurality of irregular valleys and peaks.

1. A color-separating framed silk screen including a continuous framewhich forms a circumscribed frame area, a silk screen secured to saidframe and stretched over said circumscribed area, said screen havingareas which are pervious and impervious to fluid material, a thinflexible, elongated separator strip fastened to parts of the frame andhaving a bottom edge secured to the screen to provide separated colorareas, one of said fluid pervious areas being a linear pervious area inthe screen adjoining the bottom edge of said strip, said linear areabeing pervious to a fluid adhesive material, and a bonded joint formedby said cured adhesive material holding said bottom edge to said screenby extending into said linear pervious area.
 2. A framed silk screen asin claim 1 wherein said bonded joint comprises a cured flexible resin,and said flexible resin bonded joint extends continuously along saidbottom edge and linear pervious area.
 3. A framed silk screen as inclaim 1 in which said strip extends to opposite frame parts, and theopposite ends of said flexible separator strip are fastened to saidopposite frame parts.
 4. A framed silk screen as in claim 1 wherein saidflexible separator strip is a plastic strip which is substantially inertto printing ink which contacts said strip.
 5. A framed silk screen as inclaim 1 which further includes a roughened area along the lower edge ofsaid flexible separator strip to increase the surface area to enhancethe bonding action at said bonded joint.
 6. A framed silk screen as inclaim 1 wherein said frame is rectangular and includes a plurality offrame members comprising longitudinal side members joined at theiropposite ends by shorter end members, the respective ends of saidmembers being spliced to one another, said silk screen having arectangular area, a slit provided in each of the opposite end members,the opposite ends of said flexible separator strip extending into saidslits and being fastened therein, and said bonded joint holding saidbottom edge of the flexible separator strip to the screen, said bondedjoint extending continuously between said opposite end members.
 7. Aframed silk screen as in claim 5 wherein said roughened area along thebottom edge of said flexible separator strip to increase the bondingarea comprises a row of holes with projecting, broken flange portions.8. A framed silk screen as in claim 5 wherein said roughened areacomprises an irregular rough surface.
 9. A framed silk screen as inclaim 8 wherein said roughened area is a knurled surface having aplurality of irregular valleys and peaks.